"OB" in the context of masterbatches for packaging typically refers to Optical Brightening (OB) or Optical Brightening Agents (OBAs). Optical brighteners are additives used in the plastics industry to enhance the appearance of packaging materials by increasing their perceived whiteness or brightness. OB masterbatch is used in packaging to improve the visual appearance of white or light-colored plastic materials. It can make packaging appear cleaner, fresher, and more attractive to consumers.

When OBAs are added to packaging materials, they absorb UV light and emit visible light, which makes the packaging material look brighter and more vivid. This effect is often desired in products like detergents, paper products, and certain food packaging.